We may be the world's only remaining superpower, but we've been a secondary factor in the wave of change sweeping the Arab world.

Tunisia held its revolution without American help, unless you count Facebook and Twitter. In Egypt, President Obama probably helped speed Hosni Mubarak's departure by withdrawing his backing of the regime, but it was the Egyptians' revolution, not ours.

In Syria, a repressive regime is shooting demonstrators despite escalating U.S. financial sanctions. In Bahrain, a conservative monarchy backed by Saudi Arabia has cracked down on opposition groups, blocking American attempts to mediate.

In Libya, the United States is part of an alliance that's trying to topple Moammar Kadafi, but it hasn't succeeded yet. And in the conflict between Israel and the Palestinians — the traditional focus of U.S. diplomacy in the area — Obama has been notably unsuccessful in moving negotiations forward.

The president's speech Thursday was an attempt to set out a more coherent framework for American involvement in the Middle East and North Africa. His goal was not only to make the administration's actions more understandable and effective but also to stave off the potential disasters looming on the horizon.

Many of Obama's words were about hope. "After decades of accepting the world as it is … we have a chance to pursue the world as it should be," he said.

But part of his motivation was fear. In the minds of the president and his aides, there are plenty of unpleasant scenarios that could erase the exhilaration of spring.

The still-incomplete democracies in Egypt and Tunisia could stall in the face of economic stagnation. Egypt's military leaders could decide that authoritarian rule works better than democratic disorder. The autocracies in Syria and the Persian Gulf could succeed in crushing opposition movements, teaching other regimes that repression works if it's harsh enough.

The first part of Obama's message was an attempt to assure democrats in the Arab world that U.S. backing will be more consistent than in the past. "Our support for these principles is not a secondary interest," he said. "It will be the policy of the United States to promote reform across the region, and to support transitions to democracy."

But Obama also promised to renew his efforts, fruitless so far, to restart peace negotiations between Israel and the Palestinians — a pursuit he considers even more urgent now, precisely because of the changes in Egypt and elsewhere.

For as more Arab countries turn toward democracy, there's no guarantee that the regimes that emerge will support American goals — especially peace with a Jewish state under the uncompromising leadership of Benjamin Netanyahu. Quite the contrary: It will be easy and enticing, U.S. officials fear, for the next generation of Arab politicians to take a harder line on the question of Palestinian rights as a way of bolstering their popularity.

Palestinian Authority leader Mahmoud Abbas says he will ask the U.N. General Assembly to recognize a Palestinian state this September, a move both Israel and the United States oppose. If Abbas follows through, every Arab regime — democratic or otherwise — is almost certain to support him. The result would be an old-fashioned confrontation between the United States and its new Arab friends.

Progress on peace talks, or at least evidence that the United States is pushing for progress, won't just make the U.S. relevant again; it might also help avert a spiral that could even lead to another Arab-Israeli war.

In his proposal for new talks between the Israelis and Palestinians, Obama sought to be evenhanded — by throwing punches at both sides. He said a peace settlement should be based on Israel's 1967 borders with negotiated changes, a principle Netanyahu hates to hear even though it's been de facto U.S. policy for years. Obama said the Palestinians need to abandon their drive for U.N. recognition and make their acceptance of Israel's right to a secure existence more explicit, points that drew complaints from Abbas' side.

And he proposed a path forward, suggesting that negotiations start by focusing on issues such as borders and security measures, postponing discussion of the issues that have blocked progress in the past: the future of Jerusalem and the right of Palestinians to reclaim property that their families lost when the Israeli state was established.

The president issued Netanyahu an unusually pointed warning: "The status quo is unsustainable.... Endless delay won't make the problem go away."

The question now, of course, is how Obama will follow up. Not only have Israeli-Palestinian negotiations been suspended; the United States doesn't even have a chief negotiator, now that the patient but unsuccessful George J. Mitchell has resigned. A presidential election year is an inauspicious time for any president to launch a peace effort in the Middle East, particularly since Republican candidates have already started (absurdly) accusing Obama, in Mitt Romney's words, of "throwing Israel under a bus."

So Obama's warnings of a bumpy road ahead were appropriate.

"There's no straight line to progress, and hardship always accompanies a season of hope," he said. "We must proceed with a sense of humility."

Last week, addressing the most important international drama of his presidency, Obama promised a move from improvisation to action based on a coherent policy. But until he has a strategy that's working, the president is right: We have much to be humble about.